A known fluid control valve includes a body portion provided at a circulation flow passage circulating fluid between an internal combustion engine and a heat exchanger, an inflow passage causing the fluid to flow into the body portion, an outflow passage causing the fluid to flow out of the body portion, a valve element adjusting a flow rate of the fluid, a valve seat including a contact portion relative to the valve element, the contact portion facing a downstream side of a circulating direction of the fluid, and a solenoid causing the valve element to make contact with the valve seat in a state where the solenoid is supplied with an electric power.
In a cooling apparatus cooling the internal combustion engine, i.e., an automotive engine, for example, the aforementioned fluid control valve is provided at the circulation flow passage circulating cooling water serving as fluid between the internal combustion engine and the heat exchanger so as to control a flow rate of the cooling water that is heated at the internal combustion engine to the heat exchanger, for example, to a heater core. JP2012-97835A, which will be hereinafter referred to as Reference 1, discloses a fluid control valve including a spring that biases a valve element to make contact with a valve seat so that a valve-closed state in which the valve element is in contact with the valve seat may be held in a state where a solenoid is not powered.
According to the known fluid control valve such as disclosed in Reference 1, for example, in a case where the solenoid is not powered, the valve-closed state is maintained until a fluid pressure at the inflow passage increases to a value that overcomes a biasing force of the spring. Therefore, while the fluid pressure at the inflow passage is increasing to the value that overcomes the biasing force of the spring, the fluid is inhibited from circulating. As a result, a flow rate range in which the flow rate of fluid is controllable may decrease. In addition, because a pressure-receiving area of the valve element that receives the fluid pressure at the inflow passage rapidly increases in association with a separation of the valve element from the valve seat, a gap or a clearance between the valve element and the valve seat increases rapidly, which may lead to an unstable flow rate control at a time of a low flow rate of fluid. Further, in a case where a metal touch occurs in the contact of the valve element relative to the valve seat, rust may be generated due to electrochemical reaction, for example. In such case, the valve element and the valve seat may adhere to each other, which inhibits timely controlling the flow rate based on the increase of the fluid pressure or which deteriorates a shut-off function of the valve element because of rust that adheres to the valve element and/or the valve seat.
A need thus exists for a fluid control valve which is not susceptible to the drawback mentioned above.